Continuous process for the liquid ammonia treatment of fabrics

ABSTRACT

The disclosure relates to a continuous process for the treatment, with liquid ammonia, of moving webs of fabric, the fabric having at least a partial content of natural or regenerated cellulose fiber. Fabric in substantially continuous web form is guided into a treatment chamber and there impregnated with liquid ammonia, desirably by immersion in a bath thereof. The advantageous effects of the liquid ammonia reaction are substantially realized, while undesirable excessive shrinkage of the fabric is avoided, by strictly limiting the time within which liquid ammonia reactions may occur and controllably terminating the reaction at the end of the controlled period. In the process of the invention, the liquid ammonia reaction period commences when the fabric is first introduced into the bath of liquid ammonia and is controllably terminated by bringing the ammonia-saturated web of fabric into contact with a heated drum. As a significant feature of this invention, the reaction period for a fully saturated fabric web is controlled to have a duration of between 0.6 and 9 seconds. 
     Pursuant to one aspect of the invention, a fabric web is conveyed through a processing zone under controlled lengthwise or warp-direction tension, while substantially free of tension in the width or filling direction. The precise duration of the liquid ammonia reaction period, within the specified overall range of 0.6 to 9 seconds, is controlled to achieve a desired level of residual shrinkage of the fabric in the filling direction. Residual shrinkage of the fabric in the warp-direction is controlled to desired levels by desired control of the lengthwise tension of the fabric. After termination of the reacting period, the fabric web is exposed to further processing, including continued heating and, in most cases, steaming, to rid the fabric of interstitial ammonia and to effect release of the ammonia-cellulose bonds. 
     The process of the invention enables a fabric to be processed rapidly and economically, to achieve many desirable effects of mercerization, while at the same time maintaining ammonia-induced shrinkage of the fabric.

RELATED APPLICATIONS

This application is a continuation-in-part of our copending applicationsSer. Nos. 249,736, filed May 2, 1972, now abandoned and Ser. No.346,007, filed Mar. 29, 1973, the before mentioned copendingapplications in turn being divisions of our now-abandoned earlierapplication Ser. No. 106,514, filed Jan. 14, 1971. The presentapplication is also a continuation-in-part of our copending applicationSer. No. 379,652, filed July 16, 1973, now U.S. Pat. No. 3,915,632, saidlast mentioned application being a continuation-in-part of our beforementioned application Ser. No. 106,514. This application is also relatedto our copending application Ser. No. 393,604, filed Aug. 31, 1973, nowabandoned and to the application of Jackson Lawrence, Ser. No. 490,202,filed July 19, 1974, now abandoned.

BACKGROUND OF INVENTION AND PRIOR ART OF INTEREST

The treatment of cellulose-containing fabrics with liquid ammonia hasbeen known for a long period of time. For example, mercerization ofcellulosic textile materials with liquid ammonia forms the subjectmatter of British Pat. No. 374,791 having a priority date (Germany) ofApr. 1, 1931. Since that time, a variety of patents and publications,many of which are identified herein below, have described variousprocesses and techniques for the treatment of fabrics, yarn, and threadswith liquid ammonia for various purposes.

Notwithstanding the substantial development effort which has taken placeover the years, liquid ammonia processing has not had any significantcommercial success in connection with the mercerizing or other finishingtreatment of fabrics. Primarily, this has been due to the enormousamount of shrinkage which is induced in the fabric by reaction with theliquid ammonia processing fluid. Notwithstanding the other desirableeffects achieved by the liquid ammonia reaction, the "loss" of yardagein the treating process has been so great as to substantially precludethe practical use of liquid ammonia processing in commercial finishinglines.

Significant advancement in techniques of liquid ammonia processing isreflected in the Lindberg et al. U.S. Pat. No. 3,406,006, for example,in which working relationships are sought to be established betweenapplication of controlled tension to the fabric, in relation to theamount of processing time, as a means of avoiding excessive shrinkage.However, this approach has important limitations in the context of acommercial finishing line, in which fabric is being processedcontinuously in web form. The application of tension in the width orfilling direction, to a continuously moving web of fabric, is fraughtwith difficulty and complications. Thus, the invention of the Lindberget al. patent, while constituting an interesting and significantadvance, has not resulted in widespread commercial utilization of liquidammonia processing techniques, because of the attendant problems incontrolling shrinkage loss.

Other patents and publications of interest, dealing with liquid ammoniaprocessing of fabrics, are as follows: Mahn U.S. Pat. No. 1,998,551,Estes U.S. Pat. No. 3,347,963, Webb U.S. Pat. No. 3,511,591, Gailey U.S.Pat No. 3,560,140, Troope et al. U.S. Pat. No. 3,589,030, Skaathun etal. U.S. Pat. No. 3,664,158, Calamari, Jr. et al. U.S. Pat. No.3,724,243, Calamari, Jr. et al. U.S. Pat. No. 3,767,359, Calamari, Jr.et al. U.S. Pat. No. 3,849,067. Gogek Canadian Pat. No. 810,572. GreatBritain Pat. No. 841,401. "Effect of Preswelling on Durable-PressPerformance of Cotton", Textile Research Journal, June 1969, pp. 543-7.

SUMMARY OF THE INVENTION

The present invention is based upon the discovery that the advantageouseffects of liquid ammonia processing of a cellulose-based fabric may beachieved in a commercially practicable process, without suffering thenormally attendant disadvantages, by positively limiting the time periodprovided for the liquid ammonia reaction to an extremely short time ofbetween 0.6 and 9 seconds. In this connection, we have discovered thatthe reaction of liquid ammonia with cellulosic containing fabricsproceeds largely as if in two phases. While there is overlap in thesephases, they occur to a large extent in a time sequence. In the initialphase, the cellulosic fibers are caused rapidly to swell and become moreaccessible chemically. In the second phase, the fabric continues toshrink but with little additional fiber swelling. We have establishedthat the mercerizing effects of the liquid ammonia treatment, whichresult in increased swelling and accessibility, are achieved withextreme rapidity, sometimes within a fraction of a second and in mostcases within a period of less than three seconds. Thereafter, shrinkageof the fabric is experienced on a progressive, time-related basis. Someadditional fiber swelling may occur during the second phase, but thisproceeds at a slower rate than in the first phase. Moreover, the degreeof swelling achieved in the first phase typically is amply sufficient toconstitute an acceptable level of mercerization according to industrystandards.

In the process of the invention, depending upon the requirements of theprocessor, the fabric may be treated to achieve primarily mercerizationeffects, or the processing may be extended to provide controlledshrinkage. In either case, the duration of the period in which theliquid ammonia is permitted to react significantly upon the fibers isstrictly controlled and limited to a period under nine seconds, usuallysubstantially under nine seconds. In this respect, it is to beunderstood that the specific treatment accorded to different fabrics mayvary rather widely, within the indicated control reaction period of 0.6to 9 seconds. Some fabrics, with an open construction and a relativelylow weight per unit of area, may react at a high rate of speed and maybe effectively processed in the lower end of the processing time range.Other fabrics, of heavy, close-woven construction, for example, mayrequire near maximum treatment times, within the controlled period, toachieve the desired effects. The specific processing times applicable toany specific fabric, to achieve a specific end result, have to bedetermined empirically. Nevertheless, in each case the basic principleof the invention is applicable, that of positively limiting the durationof the reaction period and thereby to control and limit the second orshrinkage phase of the reaction.

In the treatment of fabric web material in a practical commercialprocessing line, the fabric is treated in a continuous or substantiallycontinuous fashion. Thus, web material may be supplied from relativelylarge rolls thereof, and the processing is continuous at least for theindividual rolls of fabric. Successive rolls may be connected end toend, so that the tail end of a first roll draws the leading end of asuccessive roll through the processing sequence for greater continuityof processing. Insofar as this application is concerned, the term"continuous" is intended to include the continuous processing of eithersingle or successive batches of web material, whether in roll form,folded batches or otherwise. The term "continuous" is generally intendedto exclude, however, the processing of small fabric sections, such asindividual garments or individual garment sections, for example, exceptinsofar as such small fabric sections may be connected together in acontinuous string or web for processing purposes.

In the continuous processing of a fabric web according to the invention,the web is, out of practical necessity, maintained under at least aminimum warp-wise tension, in order to be able to draw the fabriccontinuously and under control through the processing chamber. In thewidth direction, however, the application of tension is difficult toapply and control, and thus the invention contemplates processing theweb material in the absence of such width-wise tension. On the otherhand, the process of the invention should not be construed to requirethe absence of width-wise tension, but rather to eliminate the necessityfor it.

In the new process, a web of fabric, in substantially dry form isconveyed into a processing chamber and there conveyed into and through abath of substantially anhydrous liquid ammonia. Desirably, the processis carried out at or slightly below atmospheric pressure, in which casethe liquid ammonia is maintained at a temperature of around minus 33° C.After momentary immersion, the web of fabric is passed through a paddingnip, to assure thorough impregnation of the fabric by the processingliquid, and the fabric is then conveyed through a controlled path intocontact with a heated dryer drum. The dryer drum is maintained at asubstantially elevated temperature, such that the cold liquid ammonia iscaused to quickly flash off, rapidly terminating the reacting of theliquid ammonia with the cellulosic fibers of the fabric. Although aconsiderably greater period of time may be required to remove all of theinterstitial ammonia and the ammonia-cellulose bonds, it is believedthat the shrinkage reaction is terminated almost instantly (e.g., withina small fraction of a second) after the fabric is brought into contactwith the heated dryer roll. Thus, for the purposes of this application,the reaction period is deemed to commence when the fabric web enters theliquid ammonia and to terminate when the fabric contacts the heatedroll. Precise control over the ammonia reaction is, according to theinvention, effected by variably controlling (within the limits of 0.6 to9 seconds) the time interval between immersion of the fabric and contactthereof with the heated roll and, to greatest advantage, this isaccomplished by varying in a controllable manner the length of the pathto which the fabric is guided in travelling from the immersion vessel tothe dryer drum.

Where controlled preshrinkage is an objective of the treatment, thereaction time is controlled to achieve the desired degree of shrinkagein the width direction, with the fabric substantially in a tension-freestate in the filling direction. Typically, shrinkage in the lengthdirection tends to proceed at a much greater rate during the reactionperiod, and the process of the invention contemplates applyingcontrolled tension to the fabric in the lengthwise direction, as a meansof limiting the lengthwise shrinkage to a desired level during thetension-free shrinkage of the fabric in the width direction.

For a more complete understanding of the above and other features andadvantages of the invention, reference should be made to the followingdetailed description and to the accompanying drawing.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a highly simplified, schematic representation of a processingline suitable for carrying out the process of the invention.

FIGS. 2 and 3 are simplified representations of modified arrangementsfor the processing of fabric according to the invention.

FIGS. 4 and 5 are time-tension graphs illustrating typical shrinkagereaction of a 100% cotton fabric treated with anhydrous liquid ammonia.FIG. 4 reflecting shrinkage in the warp-direction and FIG. 5 reflectingshrinkage in the filling direction.

FIG. 6 is a graphic representation reflecting mercerizationeffectiveness in relation to treatment time, for the processing of a100% cotton fabric with anhydrous liquid ammonia.

FIGS. 7-10 are highly magnified photographic cross sectional views oftreated and untreated cotton yarn, illustrating the effects of treatmentwith anhydrous liquid ammonia.

FIG. 11 is an enlarged, schematic representation of a portion of theprocessing system shown in FIG. 1, illustrating the manner in whichprocessing time and warp-direction tension is controlled pursuant to theinvention.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

In the processing of cellulosic-based fabrics or yarns (i.e.,constructed entirely or in part of natural or regenerated cellulose) oneor more of a combination of processing results may be sought. Thus, thereaction of cellulosic fibers with liquid ammonia causes the fibers toswell radially and become more porous. This imparts to the fiber orfabric an improved affinity for many finishing agents, such as dyes,flame retardants, resins and the like. These are mercerizing effects,which are frequently desired in the fabric finishing procedure. Inaddition to mercerizing, liquid ammonia processing of cellulosic fabricsresults in a strong tendency toward lengthwise shrinkage of the fabric.In the past, this shrinkage tendency has limited the usefulness ofliquid ammonia processing in commercial operations, because of excessiveloss of fabric through shrinkage in area. However, pursuant to theinvention, if the reaction time of the liquid ammonia on the fabric isstrictly limited, the desirable mercerizing effects are achieved,without the accompanying shrinkage. This is reflected in thephotomicrographs of FIGS. 7-10 and the graphs of FIGS. 4-6. Thephotomicrographs of FIGS. 7-10 were taken from random yarns selectedfrom a sample of cotton fabric, hereinafter identified more specificallyin connection with Example I. The selected yarns, after treatment, weremounted and then sliced into thin wafers in a plane normal to the fiberaxes. The photomicrographs were taken at 500 magnifications, using lighttransmitted through the samples.

In the photomicrograph of FIG. 7, an untreated control fabric is shown,which reveals the typical bean-like shape of the representative fiber.The photomicrograph of FIG. 8 shows a sample which has been exposed to a1 second reaction period with liquid ammonia. This shows a number offibers on the outer surface of the yarn to be already swollen. In FIG.9, the photomicrograph illustrates the yarn after a reaction period offive seconds, showing a substantial increase in the number of swollenfibers. The photomicrographs of FIG. 10, showing a yarn exposed to areaction period of 30 seconds, reflects continued swelling of thefibers, but it is evident that the additional swelling reflectedbetween, for example, FIGS. 9 and 10, is not in proportion to theadditional time.

With reference now to FIG. 6, a standard industry test for effectivenessin mercerizing is covered by test procedure AATCC 89-1958T. The test isbased on the fact that mercerized cotton absorbs more barium hydroxidethan does untreated cotton. Thus, the amount of barium hydroxideabsorbed by the sample, in relation to an untreated control, provides abasis for calculating a so-called barium activity number. Pursuant tothis test, a barium activity number of around 100 to 105 would indicatesubstantially no mercerization, while a number above 150 would indicatesubstantially complete mercerization. Typically, a barium activitynumber in the range of 150 to 160 would be considered by the trade toreflect effective mercerization. Thus, the graph of FIG. 6 reflects anenvelope of data taken on 100% cotton fabric samples (according toExample I) treated with liquid ammonia for various time periods rangingfrom zero to 3.0 seconds of reaction time as herein defined. Asreflected in the graph of FIG. 6, an adequate level of mercerization forcommercial finishing purposes is achieved within a reaction period ofvery short duration. In the initial stage of the reaction period, theslope of the barium activity curve is extremely steep, so that a bariumactivity level of 150 is achieved in a reaction period of less than 1second. Thereafter, the barium activity curve increases along arelatively shallow slope, during a second phase of the reaction period.

Now, with reference to FIG. 5, the cotton fabric of Example I, whenexposed to the liquid ammonia reaction under various levels of widthtension. The fabric used in the test of Example I was a 100% cottonbroadcloth weighing 3.5 ounces per square yard and having 136 threadsper inch in the warp and 64 threads per inch in the filling. The yarncount of the fabric was: warp, 40 singles; filling, 28 singles.Potential shrinkage of the untreated fabric by test method AATCC-135was: warp, 11.0%; filling, 0.9%. Potential shrinkage by test methodCCC-T-191a was: warp, 8.5% filling, 2.1%. The graph of FIG. 5 showsthat, at five pounds of width tension, little or no width shrinkageoccurs in a 10 second reaction period. With 2 pounds per lineal inch ofwidth tension applied, some shrinkage commenced after one second, andshrinkage continued progressively throughout the 10 second period. Withone-fourth pound tension, shrinkage commenced immediately, and after tenseconds almost the entire potential shrinkage of two percent hadoccurred. By extrapolation, shrinkage with a zero width tension would beexpected to be slightly greater than indicated for one-fourth pound oftension.

Pursuant to the invention, since effective mercerization of the fabricsample of Example T is complete in less than a second, fabric widthshrinkage can be readily held to less than the maximum potentialshrinkage of the fabric, even in the absence of width tension, byterminating the ammonia reaction at an appropriate time after completionof the initial phase of the reaction period and within the 9 secondsmaximum period contemplated by the invention.

Referring now to FIG. 4, a family of curves reflects the shrinkage inpercent of the fabric sample of Example I for various times undervarious amounts of lengthwise tension stated in pounds per lineal inch.For example, if the reaction period provided for is 4 seconds,lengthwise shrinkage of the fabric may be held to under three percent,if that is desirable, by maintaining the fabric under a warp-directiontension of three pounds per lineal inch during the reaction period.

According to one aspect of the invention, the duration of the reactionperiod is determined by the desired or tolerable degree of widthwiseshrinkage to be realized, under substantially no-tension conditions.This will establish the time of the reaction period. With the reactionperiod this fixed in duration, the desired or tolerable amount ofwarpwise shrinkage is determined, and an appropriate amount of warpwiseprocessing tension is applied to the fabric during the reaction suchthat the calculated percentage of warpwise shrinkage results during theindicated reaction period. Typically, the fabric finisher will havepredetermined shrinkage tolerances which he seeks to achieve (i.e., acertain amount of residual washing shrinkage usually is tolerated) andthese processing conditions usually may be readily achieved by workingwithin the parameters of the new process.

With reference now to FIGS. 1 and 11, there is illustrated schematicallya typical processing line for carrying out the method of invention. InFIG. 1, the untreated fabric 10, taken from a roll or other batch supply(not shown) and in substantially dry condition, is passed over smoothingrolls 11 and then around a plurality of heated dry cans 12. The dry cansare considered desirable in a commercial line, in assuring an adequatelevel of dryness in the fabric and, of more general significance,assuring greater uniformity of moisture content. In this respect, theliquid ammonia reactions optimally require a water content of less than10 percent in the ammonia at the time of reaction. Since the ammoniaabsorption of the fabric typically may be 100% of its dry weight, themoisture content of the fabric should in no instance be more than 10percent, and desirably the fabric moisture level should be well belowthat in order that the process can tolerate some content of water in theimmersion bath. Thus, the dry can 12 serve to assure that the moisturecontent of the fabric is well below 10 percent and, assuming that theincoming fabric from the supply is in the first instance well below tenpercent, the dry cans will tend to assure greater uniformity in moisturecontent from point to point on the web and thus greater uniformity inthe processing itself.

Desirably, after passing over the dry cans 12, the fabric is cooled by afan 13 prior to entering the processing chamber 14. The cooled fabricpasses over smoothing rollers 15, which also serve to pre-tension thefabric somewhat, and the fabric then passes through a gas lock 16 intothe interior of processing chamber 14. The interior 17 of the chambertypically is maintained at a slightly negative (e.g., one-half inch ofwater) pressure, in order to minimize the escape of ammonia gas, and thegas lock 16 typically may be a two-stage lock, the interior which ismaintained under an even slightly more negative pressure, so as to avoidleakage of air into the interior of the treating chamber. Such gas locksare well known, and an advantageous form thereof is shown, for example,in the copending application Ser. No. 490,199 of Jackson Lawrence, filedJuly 19, 1974.

After entering the treatment chamber, the fabric 10 passes over a guideroller 18 (see FIG. 11) and is directed downward and around an immersionroll 19. The immersion roll is disposed in the lower portion of a liquidpan 20, which retains a body of anhydrous liquid ammonia 21. The liquidammonia bath 21 typically is at a temperature of minus 33° C. and,pursuant to the process, is maintained to have a minimum water contentunder (and preferably well under) 10 percent by weight. The fabric 10,after passing around the guide roll 18, downward into the liquid ammoniabath, and around the immersion roll 19, is directed upward through thebath and about a further guide roller 22.

In a typical commercial processing operation, the fabric web 10 isadvancing at a rate such that its immersion in the liquid ammonia bath21 may be for a duration of only a fraction of a second. In thisconnection, however, while the reaction period as defined hereincommences with the entry of the fabric web 10 into the liquid ammoniabath, it does not terminate with the removal of the web from the bath,inasmuch as the web remains saturated with liquid ammonia after leavingthe bath. In the steady-state condition of the processing chamber 14,the atmosphere within the chamber is saturated with ammonia vapor, suchthat the liquid ammonia does not tend to evaporate readily from theimpregnated fabric emerging from the bath 21.

As reflected in FIG. 11, the impregnated fabric passes around the guideroller 22 and is directed into a pair of resiliently surfaced padrollers 23, 24, which are mounted to apply adjustable rolling pressureto the fabric. The pad rollers 23, 24 serve two purposes: one, toexpress from the fabric excess amounts of the liquid ammonia; two, toassure that the fabric is thoroughly penetrated by the liquid ammonia,so that the reaction proceeds uniformly. Desirably, the guide roll 22 isa bowed roller, which serves to smooth and flatten the fabric in awidthwise direction before it enters the pad rollers. In thisconnection, however, while the bowed roller 22 may momentarily apply aslight widthwise tension to the fabric, it will be appreciated that abowed roller cannot apply sustained widthwise tension to the fabric tooppose any significant tendency for the fabric to shrink in the widthduring the reaction period. Thus, the bowed roller 22 (more than one maybe utilized, if desired) serves primarily a smoothing function ratherthan a width tensioning function.

In a processing sequence according to the invention, the fabric 10emerging on the exit side of the pad roller nip may contain an amount ofliquid ammonia ranging from around 20% to around 300% of the weight ofthe fabric, depending upon factors such as characteristics of thefabric, fabric speed, efficiency of removal, etc. At this time (and assoon as the fabric first enters the ammonia bath 21) the fabric is beingreacted upon by the liquid ammonia and is in the "reaction period" asdefined herein. During this reaction period, and conveniently afterhaving passed through the pad rollers 23, 24, the fabric passes over atension control roller 25. By appropriate actuator means 33 which arewell known in the trade and need not be illustrated in detail herein,the tension control roller 25 can be controllably urged toward or awayfrom the plane of the fabric web, to impart a desired amount of warpwisetension thereto.

After passing over the tension control roller 25, the fabric passesunder fixed axis guide rollers 26, 27 and over movable axis guiderollers 28, 29. Thereafter, the fabric passes around a guide roller 30and is brought into intimate pressure contact with the surface of aheated dryer drum 31 of a so-called Palmer dryer or similar facility.The dryer includes a confining blanket 32, which is maintained undertension and serves to both press the fabric tightly against the surfaceof the heated drum 31 and to geometrically confine the fabric byfrictional forces.

In the process of the invention, the dryer drum 31 typically may beheated by high temperature steam. Thus, when the fabric 10, saturatedwith liquid ammonia at minus 33° C., comes into contact with the heateddrum surface, the ammonia is almost instantly flashed off, to a level atwhich no further substantial reaction occurs, at least in terms offabric shrinkage. Thus, the reaction period is effectively terminatedalmost instantly upon contact of the fabric with the heated drum.

Because of the impracticality, in a commercial operation, of varying thespeed of an entire processing line from moment to moment, the process ofthe present invention comtemplates the provision of arrangements forcontrollably varying the length of the path through which the fabrictravels, at constant speed, while it is saturated with reactable liquidammonia. To this end, the movable axis guide rollers 28, 29, may beraised or lowered relative to the fixed rollers 26, 27. By bringing therollers 28, 29 to positions most nearly in alignment with the rollers26, 27, a fabric path of minimum length is provided between the fabricimmersion point A and the terminal point B, at which the fabric contactsthe heated drum. If it is desired to increase the reaction period, therolls 28, 29 may be raised, causing the fabric to go through a moresinuous path, and thus increasing the time required to traverse thedistance from A to B.

In accordance with one aspect of the invention, a fabric web 10 may beprocessed on a continuously controllable basis by establishingempirically a desired level of tension to be applied to the fabric inthe warp direction by the tension control roller 25. When the processingis commenced, the tension control roller 25 is adjusted by the actuatormeans 33 to apply the desired pressure to the fabric, and the amount ofsuch pressure is continuously sensed and monitored by a suitable sensingelement 34, which may be of conventional, commercially available design.Should the pressure sensing element 34 reflect less than the desiredlevel of pressure, indicating less than the desired level of warpwisetension, the position of the movable axis guide rollers 28, 29 isadjusted to increase the length of the fabric path between points A andB. This increases the duration of the reaction period slightly,permitting a slightly greater amount of lengthwise shrinkage to occur inthe fabric and thereby tending to restore the desired level of fabrictension. Likewise, if the sensing element 34 detects excess warp tensionin the fabric, the rollers 28, 29 are automatically lowered, shorteningthe reaction period and decreasing the resulting lengthwise shrinkage ofthe fabric until the desired level of warpwise fabric tension isrestored.

In a continuous operation, moment-to-moment adjustments in the durationof the reaction period are desirably accomplished entirely by means ofadjusting the position of the movable axis rollers 28, 29. In order toaccommodate a wide variety of fabrics, however, provision is of coursemade for controlling the basic speed of operation of the entire line.Thus, the nominal reaction period may be established in the firstinstance by appropriately setting the speed of the entire processingline, thereby establishing a "nominal3[ time for the fabric travelbetween the initial and terminal points A, B in the treating chamber.The movable axis rolls are then adjusted to accommodate changes ineither direction, from the nominal reaction period, so that the desiredprocessing results are reliably achieved.

In the system shown in FIG. 1, there are two dryer stages 35, 36. Inpassing about the respective dryer drums 31, 37 of the dryer stages, thefabric 10 is tightly confined and pressed against the drum surface bytension maintained in the dryer blankets 32, 38, and most of theresidual ammonia is driven out of the fabric. In this respect, althougha substantial percentage of the ammonia is flashed off substantiallyinstantly on contact of the fabric with the first dryer drum 31, causingthe operative shrinkage reactions to substantially terminate, someresidual ammonia remains entrapped in the interstices of the fabric, anda significant amount of the ammonia remains bonded with the cellulose.The fabric shows little if any tendency toward further ammonia-reactionshrinkage while traveling over the dryer stages 35, 36. Such shrinkagetendency is effectively restrained by the geometric stabilizationprovided by the confining blankets 32, 38.

Our experience indicates that not all of the residual ammonia-cellulosebonds can be thermally broken by the dryer stages 35, 36, at leastwithin the realm of a practical commercial operation. Accordingly, thesystem of the invention desirably includes an isolated steaming chamber39, which includes provisions for penetrating the fabric with steam.Typically, the residual ammonia bonds are easily broken in the presenceof moisture, so that the fabric emerging from the steaming chamber iseffectively free of residual ammonia. It will be understood, in thisrespect, that it is not vital from a processing standpoint to rid thefabric of the last vestiges of residual ammonia. However, gradualrelease of the residual ammonia from the finished fabric can result in astrong and unpleasant aroma in the finishing area. Thus, unless goodventilating facilities are available, it is usually desirable, as apractical matter, to remove as much of the ammonia as is practicablewhile the fabric remains within the closed processing chambers.

As reflected in FIG. 1, spent ammonia gases are extracted from the mainchamber and are processed for recovery. The recovery procedure does not,however, form part of the present invention. Likewise, the ammoniagas-steam mixture from the steaming chamber 39 is extracted and eitherdisposed of or processed for recovery as a low grade material.

The processing systems illustrated schematically in FIGS. 2 and 3 arederived directly from our original parent application Ser. No. 106,514,filed Jan. 14, 1971. Each of these systems, while somewhat lesssophisticated in terms of controls, is suitable for carrying out thebasic processing steps of the invention. Thus, in the system of FIG. 2,fabric 50 enters an insulated processing chamber 51 and is directedaround a first guide roller 52, downward into a bath 53 of substantiallyanhydrous liquid ammonia. The fabric then passes around a second guideroller 54 in the ammonia bath, thence upwardly around a first bowedroller 55, through a nip defined by a pair of resiliently covered padrollers 56, 57, over a second bowed roller 58 and thence into directcontact with the heated drum 59 of a Palmer or other blanket type dryerstage 60.

As in the case of the system of FIG. 1, fabric processed by the systemof FIG. 2 is thoroughly impregnated with liquid ammonia when it isimmersed in the bath 53, and this ammonia is effectively reacting on thefabric until the fabric initially contacts the heated dryer drum 59. Theinitial, substantially instantaneous, flash off of the liquid ammoniaupon contact with the dryer drum 59 effectively terminates the reactionperiod, at least insofar as significant shrinkage is concerned.Thereafter, the fabric passes around almost the entire circumference ofthe dryer drum 59, being held tightly thereagainst by the tensionedblanket 61. In the arrangement illustrated in FIG. 2, the blanket 61itself advantageously passes around a heated drum 62, so that theblanket is at an elevated temperature when it initially contacts theammonia-laden fabric.

In the system of FIG. 2, processing control is achieved almost entirelyby controlling the speed at which the fabric 50 is conveyed through theprocessing chamber.

The processing system illustrated in FIG. 3 is generally similar to thatillustrated in FIG. 2, except that a pair of pad rollers 70, 71 arearranged so that one of them, the lower roller 70, is partiallysubmerged in the liquid ammonia bath 72 and serves as a guide roller fordirecting the fabric into and through the liquid ammonia bath. The padrollers 70, 71 are so disposed that the fabric passes through thepadding nip while traveling upwardly from the liquid ammonia bath 72.This achieves two results: first, the excess ammonia is removed asquickly as practicable and flows back to the retaining pan 73; secondly,the remaining liquid ammonia is uniformly distributed and thoroughlyimpregnated throughout the fabric at an early point in the reactionperiod, tending to assure greater uniformity in the processing results.

The arrangement of FIG. 3 may also be advantageous for use in connectionwith the processing of relatively sensitive materials, requiringprocessing times at the lower end of the range of reaction timescontemplated by the invention. In this respect, the upper padding roll71 may be in the form of a hollow drum, which is maintained at anelevated temperature, such that the liquid ammonia may, if desired, bepartially or largely driven off as the fabric passes around thecircumference of the roller. Thus, in some fabrics, by reducing theamount of the retained liquid ammonia to well below 50 percent of thedry weight of the fabric, for example, the reaction rate may besignificantly slowed, at least as far as shrinkage is concerned. Whiletheoretically this could be accomplished by merely applying a greateramount of rolling pressure at the pad roll nip, for many if not mostfabrics, such pressures would be likely to damage the fiber structure.In a typical case, fabric saturated in the ammonia bath will pick uparound, say, 130% of its weight of liquid ammonia. Some fabrics mayabsorb up to 200 to 300% of their weight in ammonia. In the padding nip,this typically will be reduced to a 100%, or even down, say, 70%.Removing more of the liquid ammonia by application of padding pressurecould involve a danger of damaging the fibers of the fabric.

The process according to the invention is applicable to a wide varietyof fabrics, incorporating a cellulosic fiber or content, and enables awide variety of results to be achieved. The following Examples areillustrative but by no means limiting. In each of the Examples, thepotential shrinkage of the untreated fabric has been determined by theCCC-T-191a method. The term "liquid ammonia take up" refers to theamount of shrinkage resulting from the ammonia processing. The term"treatment time" refers to the duration of the reaction period, asdefined herein. Unless otherwise stated in the Example, Yarn Count is inthe Cotton Count system. The term "treatment tension" refers to tensionin the warp direction.

EXAMPLE 1

Fiber--Cotton; Yarn Count--Warp 7, Filling 6; Weight--14.0 oz/Y² ;Threads per inch--Warp 67, Filling 44; Treatment Time--8.0 seconds;Treatment Tension--8.0 ounces/inch; Liquid Ammonia Take-up--Warp 8.8%,Filling 4.2%; Potential Shrinkage of Untreated Fabric--Warp 15.7%,Filling 5.8%.

EXAMPLE 2

Fiber--Cotton; Yarn Count--Warp 7, Filling 10; Weight--12 oz/Y² ;Threads per inch--Warp 67, Filling 77; Treatment Time--6.0 seconds;Treatment Tension--8.0 ounces per inch; Liquid Ammonia Take-up--Warp11.0%, Filling 1.8%; Potential Shrinkage of Untreated Fabric--Warp15.6%, Filling 3.6%.

EXAMPLE 3

Fiber--Jute (Carpet Backing); Yarn Count--Warp (Jute) 15, Filling (Jute)13; Weight--8.6 oz/Y² ; Threads per inch--Warp 16, Filling 14; TreatmentTime--4.5 seconds; Treatment Tension--8.0 ounces/inch; Liquid AmmoniaTake-up--Warp 5.5%, Filling 4.8%; Potential Shrinkage of UntreatedFabric--Warp 8.0%, Filling 5.7%.

EXAMPLE 4

Fiber--Blended Fabric; Yarn Count--Warp (Denier) 31/1 50/50 PolyesterCotton, Filling (Denier) 1/150/34 100% Polyester; Weight--3.8 oz/Y² ;Threads per inch--Warp 80, Filling 64; Treatment Time--2.25 seconds;Treatment Tension--8.0 ounces per inch; Liquid Ammonia Take-up--Warp4.9%, Filling 0.8%; Potential Shrinkage of Untreated Fabric--Warp 6.6%,Filling 2.1%.

EXAMPLE 5

Fiber--Cotton; Yarn Count--Warp 8/s (Singles), Filling 8/s (singles);Weight--10.9 oz/Y² ; Threads per inch--Warp 78, Filling 46; TreatmentTime--3.0 seconds; Treatment Tension--2.0 ounces/inch; Liquid AmmoniaTake-up--Warp 3.4%, Filling 4.2%; Potential Shrinkage of UntreatedFabric--Warp 4.8%, Filling 4.8%.

EXAMPLE 6

Fiber--Polyester/Cotton 15/85 (Knit); Yarn Count--Warp 24, Filling 24;Weight--4.3 oz/Y² ; Threads per inch--Courses 36, Wales 28; TreatmentTime--0.5 seconds; Treatment Tension--2 ounces per inch; Liquid AmmoniaTake-up--Warp 1.2+%, Filling 9.4%; Potential Shrinkage of UntreatedFabric--Warp 1.4%, Filling, 10.8%.

EXAMPLE 7

Fiber--Linen; Yarn Count--Warp (lea) 2.4, Filling (lea) 1.4; Weight--7.1oz/Y² ; Threads per inch--Warp 38, Filling 24; Treatment Time--3.0seconds; Treatment Tension--4.0 ounces; Liquid Ammonia Take-up--Warp7.6%, Filling 5.5%; Potential Shrinkage of Untreated Fabric--Warp 13.2%,Filling 8.0%.

EXAMPLE 8

Fiber--Cotton; Yarn Count--Warp 7S (Singles), Filling 6S (Singles);Weight--14.8 oz/Y² ; Threads per inch--Warp 68, Filling 44; TreatmentTime--6.0 seconds; Treatment Tension--8.0 ounces per inch; LiquidAmmonia Take-up--Warp 8.0%, Filling 4.5%; Potential Shrinkage ofUntreated Fabric--Warp 13.3%, Filling 7.1%.

EXAMPLE 9

Fiber--Cotton (Corduroy); Yarn Count--Warp 16, Filling 20; Weight--9.1oz/Y² ; Threads per inch--Warp 55, Filling 195; Treatment Time--4.5seconds; Treatment Tension--4.0 ounces/inch; Liquid AmmoniaTake-up--Warp 5.6%, Filling 3.0%; Potential Shrinkage of UntreatedFabric--Warp 7.3%, Filling 3.0+%.

EXAMPLE 10

Fiber--100% Viscose; Yarn Count--Warp 20S (Singles), Filling 20S(Singles); Weight--3.6 oz/Y² ; Threads per inch--Warp 54, Filling 50;Treatment Time--3.0 seconds; Treatment Tension--2.0 ounces per inch;Liquid Ammonia Take-up--Warp 3.6%, Filling 5.1%; Potential Shrinkage ofUntreated Fabric--Warp 18.0%, Filling 7.8%.

EXAMPLE 11

Fiber--50/50 Polyester Viscose; Yarn Count--Warp 12-2 Ply, Filling 12-2Ply; Weight--4.8 oz/Y² ; Threads per inch-- Warp 82, Filling 49;Treatment Time--1.0 seconds; Treatment Tension--8.0 ounces/inch; LiquidAmmonia Take-up--Warp 0.8%, Filling 0.3%; Potential Shrinkage ofUntreated Fabric--Warp 13.7%, Filling 2.1%.

EXAMPLE 12

Fiber--100% Cotton (Sport Denim); Yarn Count--Warp 8.3, Filling 12.2;Weight--8.86 oz/Y² ; Threads per inch--Warp 64, Filling 39; TreatmentTime--1.5 seconds; Treatment Tension--8.0 ounces/inch of width;Potential Shrinkage of Untreated Fabric--Warp 14.8%, Filling 6.6%;Liquid Ammonia Take-up--Warp 6.3%, Filling 4.2%.

EXAMPLE 13

Fiber--Cotton/Rayon (Sateen); Yarn Count--Warp 22, Filling 15;Weight--10.0 oz/Y² ; Threads per inch--Warp 113, Filling 59; TreatmentTime--5.0 seconds; Treatment Tension--16 ounces/inch of width; PotentialShrinkage of Untreated Fabric--Warp 13.2%, Filling 1.2%; Liquid AmmoniaTake-up--Warp 7.5 %. Filling 3.9%.

EXAMPLE 14

Fiber--100% Cotton (Denim); Yarn Count--Warp 7.8, Filling 10.4;Weight--10 oz/Y² ; Threads per inch--Warp 72, Filling 54; TreatmentTime----6.0 seconds; Treatment Tension--4.0 ounces/inch of width;Potential Shrinkage of Untreated Fabric--Warp 19.1%, Filling 7.5%;Liquid Ammonia Take-up--Warp 7.9%, Filling 4.5%.

EXAMPLE 15

Fiber--65/35 Linen/Polyester (Tablecloth); Yarn Count--Warp 7.5, Filling7.2; Weight--6.55 oz/Y² ; Threads per inch--Warp 35, Filling 37;Treatment Time--6.0 seconds; Treatment Tension--8.0 ounces/inch ofwidth; Potential Shrinkage of Untreated Fabric--Warp 9.5%, Filling10.8%; Liquid Ammonia Take-up--Warp 6.0%, Filling 7.2%.

EXAMPLE 16

Fiber--100% Cotton (Corduroy); Yarn Count--Warp 19.2, Filling 13.4;Weight--9.56 oz/Y² ; Threads per inch--Warp 88, Filling 48; TreatmentTime--6.0 seconds; Treatment Tension--8.0 ounces/inch of width;Potential Shrinkage of Untreated Fabric--Warp 7.6%, Filling 5% approx.;Liquid Ammonia Take-up--Warp 4.6%, Filling 2.1%.

EXAMPLE 17

Fiber--Rayon (Challis); Yarn Count--Warp 20 (Singles), Filling 20(Singles); Weight--3.55 oz/Y² ; Threads per inch--Warp 54, Filling 50;Treatment Time--3.0 seconds; Treatment Tension--2.0 ounces/inch ofwidth; Potential Shrinkage of Untreated Fabric--Warp 18.0%; LiquidAmmonia Take-up--Warp 3.6%, Filling 5.1%.

EXAMPLE 18

Fiber--100% Cotton (Twill); Yarn Count--Warp 20, Filling 16.4;Weight--7.5 oz/Y² ; Threads per inch--Warp 106, Filling 59; TreatmentTime--1.0 seconds; Treatment Tension--8.0 ounces/inch of width;Potential Shrinkage of Untreated Fabric--Warp 8.3%, Filling 11.4%;Liquid Ammonia Take-up--Warp 6.8%, Filling 6.9%.

EXAMPLE 19

Fiber--65/35 Polyester/Cotton (Broadcloth); Yarn Count--Warp 37.5,Filling 37.5; Weight--3.2 oz/Y² ; Threads per inch--Warp 131, Filling71; Treatment Time--0.75 seconds; Treatment Tension--8.0 ounces/inch ofwidth; Potential Shrinkage of Untreated Fabric--Warp 7.5%, Filling 3.9%;Liquid Ammonia Take-up--Warp 2.4%, Filling 0.9%.

EXAMPLE 20

Fiber--50/50 Cotton/Rayon (Broadcloth); Yarn Count--Warp 22.5, Filling21.0; Weight--4.5 oz/Y² ; Threads per inch--Warp 85, Filling 67;Treatment Time--1.0 seconds; Treatment Tension--0.8 ounces/inch ofwidth; Potential Shrinkage of Untreated Fabric--Warp 7.4%, Filling1.5+%; Liquid Ammonia Take-up--Warp 4.3%, Filling 3.6%.

EXAMPLE 21

Fiber--100% Cotton (Drill); Yarn Count--Warp 10.3, Filling 9.3;Weight--11.0 oz/Y² ; Threads per inch--Warp 88, Filling 45; TreatmentTime--3.0 seconds; Treatment Tension--24 ounces/inch of width; PotentialShrinkage of Untreated Fabric--Warp 7.6%; Filling 3.0+%; Liquid AmmoniaTake-up--Warp 7.5%, Filling 0%.

EXAMPLE 22

Fiber--Cotton; Yarn Count--Warp 34S (Singles), Filling 36S (Singles);Weight--4.4 oz/Y² ; Threads per inch--Warp 75, Filling 63; TreatmentTime--1.0 seconds; Treatment Tension--4 ounces per inch; Liquid AmmoniaTake-up--Warp 3.3%, Filling 3.0%; Potential Shrinkage of UntreatedFabric--Warp 6.2%, Filling 1.5+%.

The process of the invention constitutes a significant advance in theart of processing cellulosic-base fabrics with liquid ammonia. Many ofthe advantageous effects of liquid ammonia processing have been knownfor a long time, yet this form of processing has not heretofore achievedany measure of widespread commerical success. Essentially, this isbecause of the extreme shrinkage problem that is customarily experiencedin the known procedures for carrying out liquid ammonia processing. Acommercial processor simply cannot accept extraordinary losses in fabricarea in the course of processing and still remain competitive.

In the past, it has been proposed to deal with the severe ammoniashrinkage problem through the application of tensions to the fabric.However, while it may be practicable to utilize tension methods in thehandling of certain limited types of piece goods, it is not a practicalapproach for the production processing of continuous yard goods, becauseof the substantial impracticability of applying tension in an effectivemanner to the moving fabric web in the width direction during theammonia reaction period. Tentering equipment is, of course, well knownfor applying width tension. However, tentering is not practicable formany fabrics and, under the best of circumstances, tentering can causesignificant fabric distortion. By making the application of widthtension unnecessary, the process of the invention permits the liquidammonia treatment to be utilized on a commercially practicable scale.

In those special cases where the construction of the fabric and/or itsprior processing are such as to make it difficult to leave residualwidth shrinkage after ammonia processing, such result may be achieved,if desired, by tentering prior to the ammonia processing, which is thencarried out in the absence of width tension.

Our present invention is based in part on the discovery that shrinkagemay be controlled effectively, at least in the width direction, by timealone. This discovery is premised on the observation that the majorityof fabrics achieve effective mercerization by liquid ammonia treatmentin an extremely short period of time, sometimes within a fraction of asecond and in most cases less than 3 seconds. After this, continuedexposure to and reaction with the liquid ammonia does not significantlyimprove mercerization but merely induces shrinkage in the length of thefiber. Thus, by controlling the reaction period in which the fabric isexposed to effective reaction by the liquid ammonia, the width shrinkagein a continuous web of fabric may be rather precisely controlled andlimited. A maximum reaction period of nine seconds has been establishedto be an effective upper limit of the liquid ammonia reaction period forthis purpose.

In this respect, it is of significance to the invention that theeffective liquid ammonia reactions with the fabric be affirmatively andabruptly terminated within the desired treatment period in order toprovide the necessary precision of control over the process.

It is deemed theoretically possible that practical means be developedfor causing the normally rapid liquid ammonia reactions with the fabricto occur at a lower rate of speed. By way of example, this might beaccomplished by precisely limiting the amount of liquid ammonia appliedto the fabric. Insofar as the reaction rate between the liquid ammoniaand the fabric may be slowed down by this or other means, certain of thebasic principles of the invention would still be applicable as regardscontrolling the reaction period to achieve acceptable levels ofmercerization while controllably terminating the reaction soon enough toavoid excessive shrinkage in the absence of width tension during thereaction period.

In the case of certain fabrics, among which corduroy is a notableexample, the tendency for shrinkage in the filling direction of thefabric, as processed up to the stage of the liquid ammonia treatment, isso great, in relation to the residual washing shrinkage, that it issometimes difficult to maintain the ammonia reaction shrinkage at alevel appropriately less than the washing shrinkage potential. In suchcases, it may be appropriate and desirable to enlarge the width of thefabric, as a preliminary treatment, so that the ammonia-processed fabricstill retains some residual washing shrinkage in the width direction.The length direction is, of course, easily controlled during thereaction period itself through the application of tension in the warpdirection. But in all cases, the liquid ammonia reactions are carriedout while the fabric remains free of tension in the filling direction.In the treatment according to Example 16, as an illustration, the cottoncorduroy material when otherwise ready for the liquid ammoniaprocessing, had a residual washing shrinkage in the filling direction ofonly about 0.3%, making it difficult to impossible to retain some degreeof washing shrinkage after the ammonia processing. Accordingly, in theinstance of this example, the corduroy fabric was tentered prior toammonia processing, increasing its width to provide for a potentialshrinkage of around 5%. The ammonia processing resulted in approximately2% take-up in the width direction, leaving a few percent of residualwidthwise shrinkage after the ammonia treatment.

In some cases, of course, it may be either acceptable or affirmativelydesirable to permit the width direction shrinkage from ammoniaprocessing to exceed the residual washing shrinkage. And, while certainimportant aspects of the invention are directed to carrying out theprocess in a manner to provide residual washing shrinkage in the widthdirection, the invention is not exclusively directed thereto nor is itlimited thereto. In the case of Examples 13 and 20, by way ofillustration, rayon-based fabrics have been processed for a sufficienttime to cause the ammonia reaction shrinkage in the width direction toexceed the residual washing shrinkage. This is sometimes desired in thecase of rayon fabrics, in order to improve the hand and/or appearance ofthe fabric. In some cases, it is appropriate to combine such a treatmentwith a subsequent mechanical compacting of the fabric in the lengthwisedirection.

Thus, it should be understood that the forms of the invention hereinspecifically illustrated and described are intended to be representativeand not limiting, and the full scope of the invention is to bedetermined by reference to the appended claims.

We claim:
 1. The process of continuously treating with liquid ammonia afabric web, formed in significant part of natural or regeneratedcellulose, characterized bya. continuously advancing a web of the fabricto and through a treating zone, b. commencing a treating reaction withinthe treating zone by progressively impregnating the advancing fabricwith liquid ammonia, c. maintaining the advancing fabric in contact withthe liquid ammonia for a predetermined reaction period, commencing withthe initial impregnation of the fabric, d. terminating the effectivereaction period by, within 0.6 to 9 seconds of the commencement thereof,commencing and continuing the rapid removal of the liquid ammonia fromsaid fabric, and e. thereafter conveying the fabric web from saidtreatment zone.
 2. A process according to claim 1, further characterizedbya. said fabric web, during said reaction period, being substantiallyfree of widthwise tension, b. the effective duration of said reactionperiod being such that width shrinkage of the web during treatment islimited to a controlled, predetermined amount, and c. the lengthshrinkage of said web during treatment being controlled and limited by,in addition to limitations imposed by the limited duration of theeffective reaction period, maintaining a controlled amount of lengthwisetension on said web as it traverses the treatment zone.
 3. A processaccording to claim 1, further characterized bya. rapid removal of theliquid ammonia being commenced and continued by conveying said web intodirect contact with a heated surface and maintaining said web inpressure contacting relation with said heated surface for a time toeliminate at least the highly reactive liquid phase of the ammonia fromthe fabric web.
 4. A process according to claim 3, further characterizedbya. said fabric web, after said quick removal step, being exposed to ahigh moisture environment to facilitate displacement from the fabric ofresidual ammonia.
 5. A process according to claim 1, furthercharacterized bya. during the period of rapid removal of at least theliquid phase of the ammonia from said fabric, said fabric beinggeometrically confined against a surface.
 6. A process according toclaim 5, further characterized bya. the rapid removal of liquid ammoniabeing effected by bringing said fabric web into contact with the surfaceof a synchronously rotating dryer drum, and b. the fabric beingsimultaneously confined geometrically and held in contact with said drumby means of a confining blanket moving synchronously with said drum. 7.A process according to claim 1, further characterized bya. said fabricbeing initially thoroughly wet out by the liquid ammonia, b. quicklythereafter subjecting the wet-out fabric to controlled rolling pressureto effect thorough and uniform penetration of the fabric by said liquidammonia and to remove excess amount of said liquid ammonia, andthereafter commencing said rapid removal.
 8. A process according toclaim 7, further characterized bya. said fabric being initially wet-outby direct immersion of the fabric in a confined body of liquid ammonia.9. The process of continuously treating with liquid ammonia a fabricweb, formed in significant part of natural or regenerated cellulose,which comprisesa. progressively delivering a web of the fabric in asubstantially dry state, b. impregnating said fabric in a treating zonewith a sufficient amount of substantially anhydrous liquid ammonia toeffect rapid mercerization of said fabric and to commence shrinkagethereof in the absence of counteracting tension, c. subsequent tosubstantial impregnation of said fabric web and prior to excessiveshrinkage thereof, and within a period of from 0.6 seconds to 9 secondsfrom impregnation of the fabric, effectively terminating the liquidammonia reaction with the fabric.
 10. The process of claim 9, furthercharacterized bya. the combined moisture content of said substantiallydry fabric and of said substantially anhydrous ammonia being notsubstantially more than about 10% of the weight of the ammonia withwhich the fabric is impregnated.
 11. The process of claim 10, furthercharacterized bya. said fabric being heated prior to impregnation toreduce its moisture content, and b. said heated fabric being cooledprior to impregnation.
 12. The process of claim 9, further characterizedbya. said fabric web being conveyed, during its period of reaction withsaid liquid ammonia, substantially free of tension in the widthdirection.
 13. The process of claim 9, further characterized bya. saidliquid ammonia reactions being effectively terminated at a time, within9 seconds of impregnation at which width direction shrinkage of the webis equal to or less than the washing shrinkage of the fabric in suchdirection.
 14. The process of claim 13, further characterized bya.during said reaction period, shrinkage of the fabric in the warpdirection is limited to an amount equal to or less than the washingshrinkage by the controlled application of tension in the warpdirection.
 15. The process of claim 9, further characterized bya. saidammonia reactions being effectively terminated by bringing said web intofull surface pressure contact with a synchronously moving heatedsurface.
 16. The process of claim 15, further characterized bya. saidfabric is maintained in continued contact with said heated surface for aperiod, subsequent to the termination of said reaction period, to driveoff residual ammonia from the fabric.
 17. The process of claim 16,further characterized bya. said fabric, subsequent to said continuedcontact, is exposed to a moisterizing medium to facilitate the furtherrelease of bonded ammonia.
 18. The process of continuously treating withliquid ammonia a moving web of fabric, formed in significant part ofnatural or regenerated cellulose, which comprisesa. progressivelyconveying the fabric web through a treating zone, b. impregnating thefabric in said zone with liquid ammonia, c. causing or permitting theliquid ammonia to react with the fabric in said zone for a periodsufficient to achieve commerically acceptable levels of mercerization ofthe fabric, and d. thereafter effectively terminating the liquid ammoniareaction before said fabric web has been shrunk in the width directionby an amount as great as its washing shrinkage, e. said fabric beingmaintained substantially free of tension in the width direction duringthe period of said liquid ammonia reaction.
 19. The process of claim 18,further characterized bya. said fabric being maintained under sufficientlengthwise tension during the period of said liquid ammonia reaction toprevent shrinkage of the fabric in a lengthwise direction in amountsexceeding the washing shrinkage of the fabric in such direction.
 20. Theprocess of claim 19, further characterized bya. the combined watercontent of the fabric and the liquid ammonia being not substantially inexcess of ten percent of the weight of the ammonia with which the fabricis impregnated.
 21. The process of claim 20, further characterized bya.said fabric being treated prior to liquid ammonia impregnation to reduceits moisture content and again after the liquid ammonia reaction toincrease its moisture content.
 22. The process of claim 18, furthercharacterized bya. said liquid ammonia reaction being effectivelyterminated by bringing the fabric web progressively into contact with aheated surface, and b. urging the fabric into pressure contact with saidsurface and maintaining such pressure contact for a period sufficient todrive off substantial amounts of the residual ammonia.
 23. The processof claim 22, further characterized bya. said heated surface comprising arotating drum, and b. said fabric being maintained in pressure contactwith said surface over the entire width of the fabric and over asubstantial circumferential area of the drum by means of a tensionedblanket moving with the drum.
 24. The process of claim 18, furthercharacterized bya. prior to impregnating the fabric with liquid ammonia,expanding the fabric in the width direction to increase its widthwiseshrinkage potential.
 25. The process of claim 24, further characterizedbya. said fabric being a cotton corduroy.
 26. The process of claim 18,further characterized bya. said liquid ammonia reaction beingeffectively terminated within 0.6 to 9 seconds after impregnation of thefabric.